Cryptology ePrint Archive: Report 2015/577

Twist Insecurity

Manfred Lochter, Andreas Wiemers

Abstract: Several authors suggest that the use of twist secure Elliptic Curves automatically leads to secure implementations. We argue that even for twist secure curves a point validation has to be performed. We illustrate this with examples where the security of EC-algorithms is strongly degraded, even for twist secure curves.

We show that the usual blindig countermeasures against SCA are insufficient (actually they introduce weaknesses) if no point validation is performed, or if an attacker has access to certain intermediate points. In this case the overall security of the system is reduced to the length of the blinding parameter. We emphazise that our methods work even in the case of a very high identification error rate during the SCA-phase.

Category / Keywords: public-key cryptography / Twist security, deterministic ECDSA, ECDH, random blinding, SCA

Date: received 9 Jun 2015

Contact author: manfred lochter at bsi bund de

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